What is an endorheic lake?

An endorheic lake, or sink lake, is a collection of water within an endorheic basin, or sink, with no evident outlet. Endorheic lakes are generally saline as a result of being unable to get rid of solutes left in the lake by evaporation. These lakes can be used as indicators of anthropogenic change, such as irrigation or climate change, in the areas surrounding them. Lakes with subsurface drainage are considered cryptorheic.

The two main ways that endorheic lakes accumulate water are through river flow into the lake (discharge) and precipitation falling into the lake. The collected water of the lake, instead of discharging, can only be lost due to either evapotranspiration or percolation (water sinking underground, e.g., to become groundwater in an aquifer). Because of this lack of an outlet, endorheic lakes are mostly saltwater rather than freshwater. The salinity in the lake gradually builds up through years as water evaporates and leaves its solutes behind.